Surveillance of T1D incidence in the U.S. has focused on youth <20 years, despite some evidence from Europe suggesting that up to half of all incident T1D cases occur in adulthood. There are very limited data in the U.S. on the incidence of T1D among individuals ? 20 years of age because diabetes is not a reportable condition. Moreover, diabetes type based on self-report has limited reliability and ascertaining diabetes type from medical record data is constrained in the relatively fragmented health care in most clinical settings in the U.S. The Diabetes in Young Adults (DiYA) study addresses these gaps by pilot testing the feasibility of developing and implementing a population-based, timely, low-cost surveillance system for the assessment of the incidence of type 1 diabetes among young adults, age 20 to 45 years in the United States.